Fluid pumping system

ABSTRACT

A fluid pumping system is disclosed that includes a housing in which a fluid flows. The fluid pumping system also includes a vane wheel that is rotatably supported in the housing and that has a plurality of vane portions. At least one of the vane portions is swept-forward such that an axial end of the at least one of the vane portions extends toward the direction of rotation of the vane wheel.

CROSS REFERENCE TO RELATED APPLICATION(S)

The following is based on and claims priority to Japanese Patent Application No. 2005-283759, filed Sep. 29, 2005, which is hereby incorporated in its entirety by reference.

FIELD

The present invention relates to a fluid pumping system with an impeller for pumping a fluid.

BACKGROUND

Secondary air supply apparatuses have been proposed in which secondary air produced by operating a motorized air pump flows to a three way catalyst converter through a secondary air channel pipe and an engine exhaust pipe to activate a three-way catalyst when an internal combustion engine is started. Japanese Patent Publication No. 11-107980 discloses such a system. A double vane type vortex flow pump (i.e., vortex pump) is usually used as the motorized air pump. The flow pump includes a housing having a pump chamber therein and a vane wheel (i.e., an impeller) that is rotatably mounted in the housing. The vane wheel has multiple vane portions (i.e., fins) rotationally driven by an electric motor.

However, conventional motorized air pumps, such as the pump described in Japanese Patent Publication No. 11-107980 suffer from certain disadvantages. For instance, the vanes of the motor air pump are perpendicular to the direction of the rotation of the impeller (i.e., the angle of incline φ of the fins is 0°). For this reason, the flow of air into and between adjoining fins falls behind the rotational speed of the electric motor (i.e., the rotational speed of the impeller). As a result, a separation vortex due to separation of the flow of secondary air is produced from the ends of the fins on the side of a suction opening to the opposite ends of the fins in the direction of rotation. This produces turbulence noise, and the noise level becomes high in all the frequency bands.

In partial response to this problem, Japanese Published Examined Application No. 2004-109909 discloses a system in which the number of fins is N and the rotational speed of a motor is S (rpm). A value, F, obtained by multiplying N and S is set to a value higher than a human audible frequency band Fh (i.e., not more than 20 kHz).

However, as represented in FIG. 6A, the multiple fins 101 are perpendicular to the direction of rotation of an impeller 102 similar to the motorized air pump described in Japanese Patent Publication No. 11-107980. In other words, the angle of incline φ of the fins is 0°. For this reason, a separation vortex due to separation of the flow of secondary air is produced from the ends of the fins 101 on the side of a suction opening to the opposite ends in the direction of rotation, as illustrated in FIG. 6B. This produces turbulence noise, which is undesirable. The main exciting force, which is highest in noise level among vortex pump noises, is the turbulence noise (20 kHz or below) in the pump chamber. However, conventional fluid pumping systems have not sufficiently reduced this turbulence noise. Specifically, as shown in the diagram of FIG. 5, the peak value of turbulence noise (noise level) in a vortex pump of the prior art is approximately 1.6 kHz. Thus, there remains a need for a fluid pump that produces less turbulence noise.

SUMMARY OF THE INVENTION

A fluid pumping system is disclosed that includes a housing in which a fluid flows. The fluid pumping system also includes a vane wheel that is rotatably supported in the housing and that has a plurality of vane portions. At least one of the vane portions is swept-forward such that an axial end of the at least one of the vane portions extends toward the direction of rotation of the vane wheel.

A vehicle secondary air supply apparatus for warming of a catalyst is also disclosed. The apparatus includes a housing in which a fluid flows. The fluid pumping system also includes a vane wheel that is rotatably supported in the housing and that has a plurality of vane portions. At least one of the vane portions is swept-forward such that an axial end of the at least one of the vane portions extends toward the direction of rotation of the vane wheel.

Furthermore, a fluid pumping system is disclosed that includes a housing in which a fluid flows and a vane wheel that is rotatably supported in the housing. The vane wheel includes an annular dividing wall, a plurality of first vane portions, and a plurality of second vane portions. The first and second vane portions are curved in the radial direction of the vane wheel. The annular dividing wall is provided between the first and second vane portions. The first vane portions are swept forward from the annular dividing wall such that an axial end of the first vane portions extend toward the direction of rotation of the vane wheel. Also, the second vane portions are swept forward from the annular dividing wall such that an axial end of the second vane portions extend toward the direction of rotation of the vane wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one embodiment of a secondary air supply system;

FIG. 2 is a sectional view of a motor air pump for use in the secondary air supply system of FIG. 1;

FIG. 3A is a front view of one embodiment of an impeller for use in the secondary air supply system of FIG. 1;

FIG. 3B is a bottom, projected view of the impeller of FIG. 3A;

FIG. 4A is a bottom, projected view of the impeller of FIG. 3A;

FIG. 4B is a sectional view of the impeller of FIG. 3A;

FIG. 4C is a bottom, projected view of another embodiment of the impeller;

FIG. 5 is a graph comparing noise level of the impeller of FIG. 3A to those of the prior art;

FIG. 6A is a bottom, projected view of an impeller of the prior art;

FIG. 6B is a sectional view of an impeller of the prior art; and

FIG. 7 is a graph illustrating the relationship between noise level and angle of incline for the impeller of FIG. 3A.

DETAILED DESCRIPTION

In general, in order to suppress the production of turbulent flows due to flow separation and thereby reduce turbulence noise, an impeller of a fluid pumping system is disclosed that includes at least one vane portion that is swept-forward and inclined toward the direction of rotation.

Referring to FIG. 1, one embodiment of a motor air pump 1 is incorporated into a secondary air supply system (i.e., secondary air supply apparatus). As will be explained, when an internal combustion engine E (e.g., a gasoline engine) is started, secondary air (i.e., fluid) flows in secondary air channel pipes 11, 12 (i.e., fluid channel pipes, air channel pipes). The secondary air supply system guides this secondary air into a three-way catalyst converter 13 to facilitate warming of a three-way catalyst. This secondary air supply system is mounted in, for example, the engine compartment of a vehicle, such as an automobile. In the secondary air supply system, the motor air pump 1 and a secondary air control valve 14 are hermetically connected to each other through the secondary air channel pipe 11. The secondary air control valve 14 and an engine exhaust pipe 15 are hermetically connected to each other through the secondary air channel pipe 12.

The engine E obtains output by thermal energy obtained by burning air/fuel mixture of intake air and fuel in combustion chambers. The engine E includes a cylinder block that slidably supports pistons 16. The engine E also includes a cylinder head with intake ports joined with the downstream end of an engine intake pipe 17 that includes an intake manifold. The engine E further includes an exhaust manifold and exhaust ports joined with the upstream end of the engine exhaust pipe 15. The intake ports and the exhaust ports are opened and closed by intake valves and exhaust valves, respectively. In the cylinder head, there are installed spark plugs 18 with tips that are exposed in the combustion chambers. Further, in the cylinder head, there are installed electromagnetic fuel injection valves 19 (i.e., injectors) that inject fuel toward intake valves.

In the engine intake pipe 17, there are intake air passages that connect to the combustion chambers of the engine E through the intake ports. Intake air sucked into the combustion chambers of the engine E flows in the intake air passages. In the engine intake pipe 17, an air cleaner 20 is included that filters intake air and a throttle valve 22 that performs opening/closing operation in correspondence with the amount of accelerator pedal 21 depression (i.e., accelerator opening). In the engine exhaust pipe 15, there are formed exhaust passages that connect to the combustion chambers of the engine E through the exhaust ports. Exhaust gas flows out of the combustion chambers of the engine E toward the three-way catalyst converter 13. An O₂ sensor 23 is supported in the engine exhaust pipe 15 and detects the oxygen concentration of exhaust gas. A catalyst temperature sensor 24 is also included that detects the temperature of the three-way catalyst. Furthermore, an exhaust gas temperature sensor (not shown) is included in the exhaust pipe 15 for detecting the temperature of exhaust gas. It will be appreciated that other sensors and the like can be included in the exhaust pipe 15.

Secondary air channels are included in the secondary air channel pipes 11, 12 for guiding secondary air, pressure-fed and supplied from the motor air pump 1, to the three way catalyst converter 13 through the engine exhaust pipe 15. The secondary air control valve 14 is an electromagnetic fluid control valve (or motor-operated fluid control valve) formed by integrating an air switching valve (hereafter, referred to as ASV) and a check valve. The ASV opens and closes the secondary air channel formed in the secondary air channel pipe 12, and the check valve prevents fluid, such as exhaust gas, from flowing from the joint between the secondary air channel pipe 12 and the engine exhaust pipe 15 back toward the ASV The check valve has a film lead valve that is opened by the pressure of secondary air discharged from the motor air pump 1.

The secondary air supply system is in communication with an engine control unit (not shown). The engine control unit (hereinafter, ECU) electronically controls an electric motor 2. The electric motor 2 is the power source of the motor air pump 1. The ECU also controls an actuator (not shown), which is the power source of the secondary air control valve 14. The ECU controls the electric motor 2 and the actuator based on the state of operation of the engine E. The ECU is provided with a microcomputer of publicly known structure. The ECU operates as a CPU that carries out control processing and computation processing, a storage device (i.e., memory such as ROM and RAM) that stores various programs and data, and the like. Furthermore, the ECU operates as a pump control unit. When the ignition switch is turned on (IG=ON), the ECU adjusts power supplied to the electric motor 2 to control the rotational motion (e.g. rotational speed) of the motor air pump 1 based on a control program stored in memory.

When the engine is started, the ECU detects the exhaust gas temperature with the exhaust gas temperature sensor. When the detected exhaust gas temperature is equal to or lower than a predetermined value, the ECU drives and opens the secondary air control valve 14. Since power is also supplied to the motor air pump 1 at this time, a secondary airflow is generated in the secondary air channels formed in the secondary air channel pipes 11, 12. The ECU has a fault diagnosis function for diagnosing anomalies and faults in the motor air pump 1. A pressure sensor 25 is installed in the secondary air channel pipe 11, and when the secondary air pressure detected by the pressure sensor 25 is out of a predetermined pressure range, an anomaly is detected.

Brief description will be given to the construction of the motor air pump 1 in this embodiment with reference to FIG. 2 to FIGS. 4A and 4B. The motor air pump 1 is a double vane type vortex motor air pump. The motor air pump 1 includes the electric motor 2 operated with electric power, a pump housing 4 coupled to the motor housing 3 of the electric motor 2, an air duct 5 hermetically joined with the pump housing 4, a filter 6 provided in the air duct 5, a pump impeller 7 (i.e., air pump body) rotatably supported in the pump housing 4 and rotationally driven by the electric motor 2, and the like.

In one embodiment, the electric motor 2 is a direct-current (DC) motor. This electric motor 2 includes a field (stator) 33 with multiple permanent magnets 32 on the inner circumferential surface of a cylindrical yoke 31. The motor 2 also includes an armature (rotor) 34 provided on the inner circumferential surface of the field 33. The motor 2 further includes a brush assembly 37 with multiple brushes 36 to be abutted against the commutator 35 provided in the armature 34 in the motor housing 3. It will be appreciated that the motor 2 could be of any suitable type, such as a brushless direct-current (DC) motor or an alternating-current (AC) motor, such as a three-phase induction motor.

The armature 34 includes a motor shaft 41 (i.e., a rotating shaft or the output shaft of the electric motor 2). The motor shaft 41 is rotatably supported in the motor housing 3. The armature 34 also includes an armature core 42 secured on the outer circumferential surface of the motor shaft 41. The armature 34 further includes multiple armature coils (i.e., armature windings) wound on the armature core 42. The armature 34 additionally includes multiple commutators 35 connected in correspondence with the respective armature coils. The brush assembly 37 includes multiple brushes 36 pressed against the commutators 35 and multiple brush holding members 44 that hold the brushes 36 toward the commutators 35 so that the brushes can slide. The brush assembly 37 further includes multiple springs 45 that energize the individual brushes 36 toward the commutators 35 and a spacer 46 that supports the brush holding members 44 in the motor housing 3.

The pump housing 4 includes a first case 52 coupled to the motor housing 3 by screws 51 and a second case 54 coupled to the first case 52 by clips 53. An annular swirl chamber 57 (i.e., pump chamber) is provided in the pump housing 4 for compressing air due to rotation of the impeller 7. The air duct 5 is connected to the first case 52 for directing the air into the swirl chamber 57. First and second C-shaped side grooves 58, 59 are provided in the peripheral portion of the swirl chamber 57 in the radial direction and have respective bottom faces with semi-circular sectional shape.

The filter 6 is provided in the air duct 5 for filtering the air sucked into the impeller 7. The filter 6 catches foreign matter mixed in air to prevent the entry of the foreign matter into the swirl chamber 57. However, air flowing in through the open end (i.e., air inlet) of the air duct 5 can pass through the filter 6. In the embodiment of the motor air pump 1 illustrated in FIG. 1, a filter case 9 is hermetically connected to the upstream end of the air duct 5, and the filter 6 is placed in the filter case 9. It will be appreciated that the filter 6 need not be placed in the air duct 5. In the first case 52, there is formed a pump suction opening 56 for sucking the air from the air channel 55 formed in the air duct 5 into the swirl chamber 57. In the second case 54, there is formed a pump discharge opening (not shown) for discharging air from the swirl chamber 57. Between the first and second cases 52, 54, there is provided a dividing plate (i.e., partitioning portion—not shown) for preventing air from directly flowing from the pump suction opening 56 into the pump discharge opening.

The impeller 7 is rotatably housed in the swirl chamber 57 of the pump housing 4. The impeller 7 is a double vane type vane wheel having a plurality of vane portions (i.e., blades, fins, etc.) and a plurality of vane grooves. The impeller 7 pressurizes the air sucked into the swirl chamber 57 and discharges the pressurized air. The impeller 7 has a disk-shaped rotor portion 61 (i.e., main body) secured on the outer circumferential surface of the axial end of the motor shaft 41 of the electric motor 2 so that the impeller 7 is unlikely to rotate relative to the motor shaft 41. On the outer radial portion of the rotor portion 61, there are formed a plurality of vane portions 62, 63. The vane portions 62, 63 are disposed in spaced relationship to each other around the circumference of the rotor portion 61. In one embodiment, the vane portions 62, 63 are equally spaced away from each other around the circumference of the rotor portion 61. (The vane portions will be hereafter referred to as multiple first vane portions 62 and second vane portions 63). Vane grooves 64, 65 are defined between the vane portions 62, 63. (The vane grooves will be hereafter referred to as first vane grooves 64 and second vane grooves 65.)

The first vane portions 62 and the first vane grooves 64 are provided on the upstream side of the secondary air flow (i.e., the right side in FIG. 2). The first vane portions 62 and first vane grooves 64 curve radially away from the rotor portion 61. As such, the first vane portions 62 and the first vane grooves 64 are concave and curved from an inner radius end to an outer radius end in the direction of the radius of the rotor portion 61. The first vane portions 62 and the first vane grooves 64 are curved toward the direction of rotation of the impeller 7 (i.e., toward the direction of the arrow in FIG. 3A and toward the direction of the arrow in FIG. 4A).

On the other hand, the second vane portions 63 and the second vane grooves 65 are provided on the downstream side of the secondary air flow (i.e., the left side in FIG. 2). As shown in FIG. 3, the second vane portions 63 and the second vane grooves 65 curve radially away from the rotor portion 61. As such, the second vane portions 63 and the second vane grooves 65 are concave and curved from an inner radius end to an outer radius end in the direction of the radius of the rotor portion 61. The second vane portions 63 and the second vane grooves 65 are curved toward the direction of rotation of the impeller 7 (i.e., toward the direction of the arrow in FIG. 3A and toward the direction of the arrow in FIG. 4A).

As shown in FIGS. 3B, 4A, and 4B, each of the first vane portions 62 include a respective first end 70 and a respective second end 72 (i.e., axial end). Also, each of the second vane portions 63 includes a respective first end 71 and a respective second end 73 (i.e., axial end). The first ends 70, 71 of the first and second vane portions 62, 63 are provided near the center of the impeller 7 in the direction of the rotational axis of the impeller 7, and the second ends 72, 73 of the first and second vane portions 62, 63 are provided on opposite axial ends of the impeller 7 in the 15 direction of the rotational axis of the impeller 7. It will be appreciated that the second ends 72, 73 of the first and second vane portions 62, 63 correspond with suction openings (i.e., leading edges, ridgelines on the upstream side in the direction of the flow of fluid) of the impeller 7. It will also be appreciated that the first ends 70, 71 of the first and second vane portions 62, 63 correspond with discharge openings (i.e., trailing edges, ridgelines on the downstream side in the direction of the flow of fluid) of the impeller 7.

As shown in FIGS. 3B, 4A, and 4B, an annular dividing wall 66 (i.e., rib) is included between the first and second vane portions 62, 63. The annular dividing wall 66 extends radially away from the rotor portion 61 and extends around the entire circumference of the rotor portion 61. The annular dividing wall 66 is provided approximately at the center of the impeller 7 in the direction of the rotational axis of the impeller 7. As shown in FIG. 2, the dividing wall 66 is wider and concave at its base such that the bottom of the first and second vane grooves 64, 65 are curved surfaces. In the embodiment shown, the curved surfaces of the dividing wall 66 are flush with the curved surfaces of the adjacent first and second side grooves 58, 59 of the swirl chamber 57.

As shown in FIGS. 3B, 4A, and 4B, the first vane portions 62 are coupled to the annular dividing wall 66 at the respective first ends 70 thereof. Also, the second vane portions 63 are coupled to the annular dividing wall 66 at the respective first ends 71 thereof.

Furthermore, as shown in FIGS. 3B, 4A, and 4B, at least one of the first and second vane portions 62, 63 are swept forward with respect to the axis of rotation of the impeller 7. In the embodiment shown, each of the first and second vane portions 62, 63 are swept forward. This means that each of the first and second vane portions 62, 63 is inclined and extends toward the direction of rotation of the impeller 7 (i.e., inclined toward the direction of the arrow shown in FIG. 4A). In other words, the second ends 72, 73 of the vane portions 62, 63 (i.e., the axial ends of the vane portions 62, 63) extend toward the direction of rotation of the impeller 7. Stated differently, the first and second vane portions 62, 63 are inclined at a positive angle (i.e., an angle of incline φ) relative to the dividing wall 66 such that the second ends 72, 73 of the first and second vane portions 62, 63 (i.e., the suction ends) are positioned ahead of the first ends 70, 71 thereof (i.e., the discharge ends) in the direction of rotation of the impeller 7.

The angle of incline φ of the first and second vane portions 62, 63 (i.e., the angle defined between the surface of the respective first or second vane portion 62, 63 and the axis of rotation of the impeller 7) is greater than zero. In one embodiment, the angle of incline φ is at least 15° and at most 30° to thereby correspond reduce noise levels as shown in FIG. 7. Further, in one embodiment, the angle of incline φ is approximately 20°.

Action of First Embodiment

Vehicles, such as automobiles, are mounted with an exhaust gas purifier. Exhaust gas discharged from the combustion chambers of the engine E of a vehicle contains harmful components. The purifier changes elements (e.g., carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxides (NOx)) from harmful components into harmless components by chemical reaction (i.e., three way catalyst converter 13). For instance, the purifier changes hydrocarbon (HC) into harmless water (H₂O) by oxidation. In the three-way catalyst, however, proper chemical reaction does not take place unless the ratio of mixture of air and fuel is equal to a theoretical air-fuel ratio when burning is carried out in the engine E. For instance, it may be required to maintain the theoretical air-fuel ration of 14.7:1. The three-way catalyst does not properly operate when the exhaust gas temperature is too low (approximately 350° C. or below for example), immediately after the engine E is started.

For this reason, when the exhaust gas temperature is low immediately after the engine is started, electric power is supplied to the electric motor 2 of the motor air pump 1. As a result, the impeller 7 is rotationally driven by the rotational motion of the motor shaft 41 of the electric motor 2 to produce secondary air in the secondary air channel pipes 11, 12. The secondary air produced by the rotating action of the impeller 7 of the motor air pump 1 is guided into the three way catalyst converter 13 by way of the secondary air channel pipe 11, secondary air control valve 14, secondary air channel pipe 12, and engine exhaust pipe 15. Thus, warming of the three-way catalyst is facilitated to activate the three-way catalyst. Consequently, when the exhaust gas temperature is low, for example, immediately after the engine E is started, the ECU drives and opens the secondary air control valve 14. (This operation is performed when the exhaust gas temperature detected with the exhaust gas temperature sensor is lower than a predetermined value, or when the temperature of the three-way catalyst detected with the catalyst temperature sensor 24 is lower than a predetermined value.) At the same time, the ECU supplies electric power (pump driving current) to the electric motor 2 of the motor air pump 1 to actuate the motor air pump 1. Thus, the pressure feed and supply of secondary air by the motor air pump 1 is started.

When the impeller 7 is rotationally driven by the rotational motion of the motor shaft 41 of the electric motor 2, the air in the swirl chamber 57 of the pump housing 4 is compressed by movement of the multiple first and second vane portions 62, 63. Since negative pressure is produced in the pump suction opening 56 of the pump housing 4, the air filtered through the filter 6 is guided into the pump suction opening 56 by way of the air channel 55 in the air duct 5. Further, since high pressure is produced in the pump discharge opening of the pump housing 4, the air pressurized in the swirl chamber 57 is discharged from the pump discharge opening.

Therefore, the air discharged from the pump discharge opening of the motor air pump 1 is fed into the three way catalyst converter 13 by way of the secondary air channel pipe 11, secondary air control valve 14, secondary air channel pipe 12, and engine exhaust pipe 15. As a result, even when the exhaust gas temperature is low immediately after the engine is started, secondary air produced by actuating the motor air pump 1 is guided into the three way catalyst converter 13. Therefore, the three-way catalyst is activated, and the exhaust gas is purified. For instance, because the hydrocarbon (HC) is changed into water (H₂O) by oxidation, the amount of hydrocarbon (HC) emitted into the air is reduced.

Effect of First Embodiment

As mentioned above, the first and second vane portions 62, 63 are swept-forward blades inclined toward the direction of rotation of the impeller 7. As such, the air inflow angle at which air flows in from the second ends 72 of the first vane portions 62 between the first vane portions 62 substantially agrees with the angle of incline φ of the first vane portions 62. Further, the air inflow angle at which air flows in from the second end 73 of the second vane portions 63 between the second vane portions 63 substantially agrees with the angle of incline φ of the second vane portions 63. As illustrated in FIG. 4B, air smoothly flows toward the first ends 70, 71 of the first and second vane portions 62, 63 without causing substantial separation. Therefore, the production of a turbulent flow due to separation from the suction side (i.e., the second ends 72, 73) of the first and second vane portions 62, 63 can be reduced, and thus turbulence noise can be reduced.

For instance, in the motor air pump 1 in this embodiment, the noise level (30-cm noise on the suction opening side) can be reduced by an amount equal to or larger than a predetermined value in all the audible frequency bands unlike the prior art pump, as indicated in the characteristic diagram in FIG. 5. Also, for this embodiment of the motor air pump 1, the peak value (at 1.6 kHz) of the turbulence noise (i.e., noise level) in the vortex pump is reduced by 2 dB from the motor air pump of the prior art.

Modifications

In the embodiment discussed above, the motor air pump 1 is connected to the upstream end of the secondary air channel pipes 11, 12 in the direction of secondary air flow that guide secondary air into the engine exhaust pipe 15. In another embodiment, the motor air pump 1 is connected at a midpoint in the secondary air channel pipes 11, 12. In still another embodiment, the motor air pump 1 is directly connected to the joint of the secondary air channel pipe 12 and the engine exhaust pipe 15. In this case, the engine exhaust pipe 15 functions as air channel pipe, and the air channel functions as an exhaust passage.

Also, in the embodiment discussed above, the impeller 7 is directly assembled to the motor shaft 41 of the electric motor 2. In another embodiment, the motor shaft 41 of the electric motor 2 and the rotating shaft of the impeller 7 are separately constructed. Further, in one embodiment, a speed reducing mechanism that reduces the motor rotational speed to a predetermined reduction ratio is installed between the motor shaft 41 of the electric motor 2 and the rotating shaft of the impeller 7.

In the above example described in connection with this embodiment, the fluid pumping system of the invention is applied to the double vane type vortex motor air pump 1. In another embodiment, the fluid pumping system of the invention is used in a single vane type vortex motor air pump. In the above embodiment, air, such as secondary air, is used as fluid. In another embodiment, gas, such as evaporated fuel or vapor-phase coolant, or liquid, such as water, fuel, oil, or liquid-phase coolant, is fluid that is pumped.

In this embodiment, all of the first and second vane portions 62, 63 are swept-forward blades inclined toward the direction of the rotation of the impeller 7. In another embodiment, less than all of the first and second vane portions 62, 63 are swept-forward blades. In another embodiment, either the first or second vane portions 62, 63 are swept-forward blades. Regardless, it will be appreciated that the noise level is reduced in all the frequency bands more than in the prior art.

Furthermore, in one embodiment represented in FIG. 4C, the first and second vane portions 62, 63 are formed such that a portion of the vane portions 62, 63 (e.g., the portion adjacent the first ends 70, 71) extends approximately parallel to the axis of rotation of the impeller 7, and a portion of the vane portions 62, 63 (e.g., the portion adjacent the second ends 72, 73) is swept forward toward the direction of rotation of the impeller 7. Thus, the angle of incline is approximately 0° adjacent the first ends 70, 71. However, the second ends 72, 73 extend toward the direction of rotation of the impeller 7. Thus, the angle of incline φ is provided only at the suction ends (i.e., the second ends 72, 73) of the first and second vane portions 62, 63. This configuration could be applied to less than all of the first and second vane portions 62, 63. This configuration could also be applied to either one of the first and second vane portions 62, 63.

While only the selected preferred embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing description of the preferred embodiments according to the present invention is provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 

1. A fluid pumping system, comprising: a housing in which a fluid flows; and a vane wheel that is rotatably supported in the housing and that has a plurality of vane portions, wherein at least one of the vane portions is swept-forward such that an axial end of the at least one of the vane portions extends toward the direction of rotation of the vane wheel.
 2. The fluid pumping system according to claim 1, wherein a portion of the at least one of the vane portions extends approximately parallel to the axis of rotation of the vane wheel and wherein an axial end portion of the at least one vane portion is swept-forward toward the direction of rotation of the vane wheel.
 3. The fluid pumping system according to claim 1, wherein the plurality of vane portions are spaced away from each other equally in a circumferential direction around the vane wheel.
 4. The fluid pumping system according to claim 1, wherein the vane wheel is rotationally driven by an electric motor.
 5. The fluid pumping system according to claim 1, wherein the at least one vane portion includes a first axial end and a second axial end, and wherein the at least one vane portion is inclined at a positive angle relative to the direction of rotation of the vane wheel such that the second axial end is positioned ahead of the first axial end in the direction of rotation of the vane wheel.
 6. The fluid pumping system according to claim 5, wherein the angle is at least approximately 15 degrees and at most approximately 30 degrees.
 7. The fluid pumping system according to claim 6, wherein the angle is approximately 20 degrees.
 8. The fluid pumping system according to claim 5, wherein suction of the fluid toward the vane wheel occurs adjacent the second axial end, and wherein discharge of the fluid away from the vane wheel occurs adjacent the first axial end.
 9. The fluid pumping system according to claim 1, wherein the vane wheel includes an annular dividing wall, a plurality of first vane portions, and a plurality of second vane portions, wherein the annular dividing wall is provided between the first and second vane portions, wherein the first vane portions are swept forward from the annular dividing wall, and wherein the second vane portions are swept forward from the annular dividing wall.
 10. The fluid pumping system according to claim 1, wherein the at least one vane portion is curved in the radial direction of the vane wheel.
 11. A vehicle secondary air supply apparatus for warming of a catalyst comprising: a housing in which a fluid flows; and a vane wheel that is rotatably supported in the housing and that has a plurality of vane portions, wherein at least one of the vane portions is swept-forward such that an axial end of the at least one of the vane portions extends toward the direction of rotation of the vane wheel.
 12. The vehicle secondary air supply apparatus according to claim 11, wherein a portion of the at least one of the vane portions extends approximately parallel to the axis of rotation of the vane wheel and wherein an axial end portion of the at least one vane portion is swept-forward toward the direction of rotation of the vane wheel.
 13. The vehicle secondary air supply apparatus according to claim 11, wherein the plurality of vane portions are spaced away from each other equally in a circumferential direction around the vane wheel.
 14. The vehicle secondary air supply apparatus according to claim 11, wherein the at least one vane portion includes a first axial end and a second axial end, and wherein the at least one vane portion is inclined at a positive angle relative to the direction of rotation of the vane wheel such that the second axial end is positioned ahead of the first axial end in the direction of rotation of the vane wheel.
 15. The vehicle secondary air supply apparatus according to claim 14, wherein the angle is at least approximately 15 degrees and at most approximately 30 degrees.
 16. The vehicle secondary air supply apparatus according to claim 15, wherein the angle is approximately 20 degrees.
 17. The vehicle secondary air supply apparatus according to claim 14, wherein suction of the fluid toward the vane wheel occurs adjacent the second axial end, and wherein discharge of the fluid away from the vane wheel occurs adjacent the first axial end.
 18. The vehicle secondary air supply apparatus according to claim 11, wherein the vane wheel includes an annular dividing wall, a plurality of first vane portions, and a plurality of second vane portions, wherein the annular dividing wall is provided between the first and second vane portions, wherein the first vane portions are swept forward from the annular dividing wall, and wherein the second vane portions are swept forward from the annular dividing wall.
 19. The vehicle secondary air supply apparatus according to claim 11, wherein the at least one vane portion is curved in the radial direction of the vane wheel.
 20. A fluid pumping system comprising: a housing in which a fluid flows; and a vane wheel that is rotatably supported in the housing, wherein the vane wheel includes an annular dividing wall, a plurality of first vane portions, and a plurality of second vane portions, wherein the first and second vane portions are curved in the radial direction of the vane wheel, wherein the annular dividing wall is provided between the first and second vane portions, wherein the first vane portions are swept forward from the annular dividing wall such that an axial end of the first vane portions extend toward the direction of rotation of the vane wheel, and wherein the second vane portions are swept forward from the annular dividing wall such that an axial end of the second vane portions extend toward the direction of rotation of the vane wheel. 